MILOR system could navigate where GPS fails

GPS is easy to jam with off-the-shelf technology. An
alternative, called MILOR, promises to succeed where GPS fails, and
it could launch commercially as soon as next year.

It's hard to discuss GPS these days without
using the word "ubiquitous". Satellite navigation directs supertankers,
airliners and minicabs. It takes hikers to the most distant peaks,
and the rest of us to the nearest pizza. It tracks valuable cargoes
and stolen cars, and guides emergency services to accident scenes.
But GPS can fail; it stops working in some places, and it's
vulnerable to interference. Now a British company has come up with
the solution: a navigation system that works where GPS fails. It's
a case of back to the future using a technology dating back to
WWII.

GPS does not extend everywhere. There are dead zones where it's
blocked by tall buildings, and it won't work indoors, in tunnels or
in underground car parks. But the biggest threat to GPS is interference. For example, it recently emerged that the 40,000
transmitters of LightSquared's new satellite broadband in the US may interfere with GPS reception.
Solar activity can also affect GPS. And deliberate jamming is also
a growing problem, with the ready availability of GPS jammers for
as little as £20 on the internet. White Van Man uses them to stop
the boss from tracing his movements; thieves use them to foil
anti-theft GPS tracking devices.

"We believe there are an increasing a number of cases where
jammers have been used by thieves to prevent stolen vehicles being
tracked," says Simon Atkinson, Business Sector Manager at Roke
Manor Ltd.

The GPS signal is very weak, the equivalent of a car headlight
over ten thousand miles away. A portable half-watt jammer is
powerful enough to overwhelm the GPS signal to every device within
its line of sight. This is why New Jersey airport's approach system
kept going down last year. The GPS-based system was being knocked
out by a trucker who regularly used the New Jersey Turnpike,
because he had a jammer to fool the GPS road toll. It took months
to catch him.

This vulnerability is causing concern in the navigation community.
GPS jamming, accidental or deliberate, could cause all sorts of
problems. As well as the obvious applications, it is increasingly
used in agriculture, and
the construction and manufacturing industries for automatically
routing deliveries and controlling stock. GPS tags are used to warn
if Alzheimer's patients wander out of designated areas, and to keep
tabs on offenders.

There is an alternative to GPS, known as LORAN, which was first
set up by the military to guide ships and aircraft during WWII. It
has been widely used by merchant shipping for decades, and was the
standard for navigation before GPS. LORAN uses ground-based radio
beacons that are far more powerful than GPS satellite transmitters,
and broadcast on a much longer wavelength. This makes LORAN
virtually impossible to jam. Performance is similar to GPS, with an
accuracy of about 20 metres. The big issue is that the LORAN
receivers used on ships are bulky and expensive.

"A traditional LORAN receiver is usually about the size of a cycle
helmet," says Atkinson. "The cost can run to thousands of
pounds."

The answer is Roke Manor's miniature LORAN receiver, called MILOR.
This is tiny by comparison, barely larger than a matchbox. Atkinson
says that when it is produced in bulk the pricing will be suitable
for consumer applications.

Roke Manor will not reveal how they have achieved this feat of
miniaturisation. However, they do have a long track record in
advanced communications and radar systems, and clearly their
expertise is applicable to LORAN receivers.

MILOR also includes an integrated GPS receiver, and switches
seamlessly between GPS and LORAN depending on availability, without
the user having to touch it.

"GPS is great when you can get it," says Atkinson. "When you
can't, for example inside buildings or car parks, you can always
use LORAN."